Protected expansion in expl3

Question

I am trying to understand whether there is a proper expl3 way to achieve the same result as the latex2e \protected@edef, that is expanding a token list while respecting the \protect mechanism of latex2e.

Using expl3 functions with an "x" type argument (e.g. \tl_gset:Nx) seems to expand everything ignoring the latex2e protection mechanism.

I seem to be able to achieve the desired goal by manually replicating the mechanisms applied by \protected@edef, that is by doing a \tl_set:Nn \protect { \noexpand\protect\noexpand } right before the "x" expansion (e.g., before the \tl_gset:Nx), but I wonder if this is the preferred method or if there are more elegant alternatives.

Answer 1

There is no equivalent of \protected@edef in expl3 as 'native' expl3 material is either fully expandable or engine-protected. As such, if you do need to take mixed LaTeX2e input and use it in expl3, you'll need to stick to the LaTeX2e mechanism

\protected@edef \l_tmpa_tl { <stuff> }